Transmissions in networks which employ a mix of different types of links are often restricted to the lowest bandwidth part of the transmission path, which thus acts as a bottleneck. In networks which employ a mix of radio transmission links and wire based links, radio transmission links are often bottlenecks.
One of the main challenges in radio transmission is achieving as much traffic capacity as is possible. Radio transmission, when compared to fiber optic transmission and other line-based transmission links, has a limited bandwidth. When it comes to radio-based Ethernet protocol transmissions, the number of packets that can be transmitted through radio transmission is limited by a maximum radio channel capacity, and the limitation greatly influences performance of the overall network.
Radio transmission of data also poses additional problems, in particular noise, which causes data errors. Digital data packets which have errors typically require a receiver to request retransmission, and a transmitter to retransmit the data packets. Errors thus add to data traffic on the network, lowering the effective bandwidth of the network.
One method of passing more data through a bottleneck is by compressing the data. Persons skilled in the art will appreciate that data packet payload can be compressed independently of data packet headers. Data packet headers typically contain routing data, such as MAC addresses, which is important for routing nodes in a network. Therefore data packet headers are typically not compressed. Data packet headers can be compressed if the routing data is not needed. For example, in point to point transmission, data packet headers can be compressed by a transmitter of the point to point link, and uncompressed by the receiver of the point to point link. The data packet headers are typically compressed separately from the payload because they are needed at different points of the transmission process.
Today, most compression methods, such as described in RFC2507 and RFC3095, deal with both IP header compression and payload compression.
Persons skilled in the art will appreciate that IP headers are part of the third layer of the seven layer OSI Basic Reference Model, termed the network layer, while MAC addresses are part of the second layer of the seven layer OSI Basic Reference Model, termed the data link layer. IP header compression is at a higher level of abstraction than MAC header compression. Different layers serve different purposes in the transmission process and their corresponding data are needed at different times.
The following references are believed to represent a state of the art:
US Published Patent Application 2005/0249222 of van Kampen et al; and
PCT Published Patent Application WO 01/67676 of Luminous Networks Inc. (US).
Various drawbacks of the state of the art are listed herein.
US Published Patent Application 2005/0249222 of van Kampen et al describes a fixed compression of a 6 byte MAC address to less than 6 bytes, using a look up table for translating a MAC address to a short representation thereof. The look up table applies to data packets comprised in an aggregated data frame. Producing an aggregate frame comprised of several data packets requires an especially large memory buffer, increases latency in a network, and, in noisy transmission links increases a probability of losing the entire aggregated frame due to transmission errors.
The disclosures of all references mentioned above and throughout the present specification, as well as the disclosures of all references mentioned in those references, are hereby incorporated herein by reference.